Synthesis and mesophase behaviour of four-ring azo-ester-azo compounds bearing two-terminal alkoxy groups in different lengths and proportions

ABSTRACT

Twenty four different homologues of the formula 4-alkoxy phenylazo phenyl 4ʹ-(4''-alkoxyphenylazo) benzoates (Im/n) were prepared and investigated for their mesophase behaviour. In these compounds, the length of the terminal alkoxy group attached to the benzoate moiety (n) varies between 8 and 16 carbons, while the length of the other alkoxy group, attached to phenolic portion, varies between 6 and 12 carbons. Their mesophase characteristics were examined via differential scanning calorimetry (DSC) and the type of the phase is identified by polarised light microscopy (PLM). Compounds newly prepared were structurally characterised by infrared, ¹H-NMR, mass spectroscopy, thermogravemetric and elemental analyses. Comparative studies were made between the prepared four-ring compounds and their corresponding previously investigated three-ring azo/ester analogues. The stabilities and mesomorphic ranges of the prepared compounds were found to be significantly higher than their three rings analogues.

GRAPHICAL ABSTRACT

KEYWORDS:

• Four-ring azo/ester/azo
• mesophase stability
• terminal alkoxy substituents
• comparison with three-ring analogues

Disclosure statement

No potential conflict of interest was reported by the authors.